There are various types of cartilage, e.g., hyaline cartilage and fibrocartilage. Hyaline cartilage is found at the articular surfaces of bones, e.g., in the joints, and is responsible for providing the smooth gliding motion characteristic of moveable joints. Articular cartilage is firmly attached to the underlying bones and measures typically less than 5 mm in thickness in human joints, with considerable variation depending on the joint and more particularly the site within the joint. In addition, articular cartilage is aneural, avascular, and alymphatic. In adult humans, this cartilage derives its nutrition by a double diffusion system through the synovial membrane and through the dense matrix of the cartilage to reach the chondrocyte, the cells that are found in the connective tissue of cartilage.
Adult cartilage has a limited ability of repair; thus, damage to cartilage produced by disease, such as rheumatoid arthritis and/or osteoarthritis, or trauma can lead to serious physical deformity and debilitation. Furthermore, as human articular cartilage ages, its tensile properties change. Thus, the tensile stiffness and strength of adult cartilage decreases markedly over time as a result of the aging process.
For example, the superficial zone of the knee articular cartilage exhibits an increase in tensile strength up to the third decade of life, after which it decreases markedly with age as detectable damage to type II collagen occurs at the articular surface. The deep zone cartilage also exhibits a progressive decrease in tensile strength with increasing age, although collagen content does not appear to decrease. These observations indicate that there are changes in mechanical and, hence, structural organization of cartilage with aging that, if sufficiently developed, can predispose cartilage to traumatic damage.
Usually, severe damage or loss of cartilage is treated by replacement of the joint with a prosthetic material, for example, silicone, e.g. for cosmetic repairs, or suitable metal alloys. See, e.g., U.S. Pat. No. 6,383,228 to Schmotzer, issued May 7, 2002; U.S. Pat. No. 6,203,576 to Afriat, et al., issued Mar. 20, 2001; U.S. Pat. No. 6,126,690 to Ateshian et al., issued Oct. 3, 2000. Implantation of these prosthetic devices is usually associated with loss of underlying tissue and bone without recovery of the full function allowed by the original cartilage and, with some devices, serious long-term complications associated with the loss of significant amount of tissue and bone can include infection, osteolysis and also loosening of the implant.
As can be appreciated, joint arthroplasties are highly invasive and require surgical resection of the entire, or a majority of the, articular surface of one or more bones involved in the repair. Typically with these procedures, the marrow space is fairly extensively reamed in order to fit the stem of the prosthesis within the bone. Reaming results in a loss of the patient's bone stock and over time osteolysis will frequently lead to loosening of the prosthesis. Further, the area where the implant and the bone mate degrades over time requiring the prosthesis to eventually be replaced. Since the patient's bone stock is limited, the number of possible replacement surgeries is also limited for joint arthroplasty. In short, over the course of 15 to 20 years, and in some cases even shorter time periods, the patient can run out of therapeutic options ultimately resulting in a painful, non-functional joint.
The use of matrices, tissue scaffolds or other carriers implanted with cells (e.g., chondrocyte, chondrocyte progenitors, stromal cells, mesenchymal stem cells, etc.) has also been described as a potential treatment for cartilage repair. See, also, International Publications WO 99/51719 to Fofonoff published Oct. 14, 1999; WO 01/91672 to Simon et al., published Dec. 6, 2001; and WO 01/17463 to Mansmann, published Mar. 15, 2001; and U.S. Pat. No. 6,283,980 B1 to Vibe-Hansen, et al., issued Sep. 4, 2001; U.S. Pat. No. 5,842,477 to Naughton, et al., issued Dec. 1, 1998; U.S. Pat. No. 5,769,899 to Schwartz, issued Jun. 23, 1998; U.S. Pat. No. 4,609,551 to Caplan et al., issued Sep. 2, 1986; U.S. Pat. No. 5,041,138 to Vacanti et al., issued Aug. 20, 1991; U.S. Pat. No. 5,197,985 to Caplan et al., issued Mar. 30, 1993; U.S. Pat. No. 5,226,914 to Caplan, et al., issued Jul. 13, 1993; U.S. Pat. No. 6,328,765 to Hardwick et al., issued Dec. 11, 2001; U.S. Pat. No. 6,281,195 to Rueger et al., issued Aug. 28, 2001; and U.S. Pat. No. 4,846,835 to Grande, issued Jul. 11, 1989. However, clinical outcomes with biologic replacement materials such as allograft and autograft systems and tissue scaffolds have been uncertain since most of these materials cannot achieve a morphologic arrangement or structure similar to or identical to that of the normal, disease-free human tissue it is intended to replace. Moreover, the mechanical durability of these biologic replacement materials remains uncertain.
U.S. Pat. No. 6,206,927 to Fell, et al., issued Mar. 21, 2001, and U.S. Pat. No. 6,558,421 to Fell, et al., issued May 6, 2003, disclose a surgically implantable knee prosthesis that does not require bone resection. This prosthesis is described as substantially elliptical in shape with one or more straight edges. Accordingly, these devices are not designed to substantially conform to the actual shape (contour) of the remaining cartilage in vivo and/or the underlying bone. Thus, integration of the implant can be extremely difficult due to differences in thickness and curvature between the patient's surrounding cartilage and/or the underlying subchondral bone and the prosthesis.
Thus, there remains a need for a system and method for replicating the natural geography of a joint using one or more implant parts that can be implanted using minimally invasive techniques and tools for making those repairs and implants and methods that recreate natural or near natural three-dimensional geometric relationships between two articular surfaces of the joint.